JPS5934102B2 - Steel material for seedling board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel material for use in seedling-raising boards that has an oxygen-containing manganese compound layer and a manganese plating layer on an ultra-thin cold-rolled steel sheet with a thickness of 50 to 150 μm and has excellent corrosion resistance and workability. be.

As is well known, approximately 70 areas of our country are covered by mountains and fields, and in order to protect the natural environment and secure resources, afforestation projects have been carried out systematically and continuously since ancient times, and in the United States, Canada,
It forms a beautiful forest with plenty of greenery comparable to Northern Europe.

By the way, when planting trees, until the seedlings have grown for several years, the seedlings are usually placed in a ball called a seedling board to protect them from the weeds that grow along with the seedlings and to protect them from the animals that appear in the mountains. Planted in the center of a simple protective screen made of paper, plastic, or painted steel.

FIG. 1 is a schematic diagram showing an example of such a seedling-growing board, and the seedling-growing board 1 normally has a notch 3 for passing the seedlings 4 through and a hole 2 provided so that the seedlings 4 are placed approximately in the center. The area of the seedling board is such that weeds cannot reach the seedlings (approximately 0.8 m2), and if necessary, it is coated with chemicals that are aversive to wild animals. be.

The purpose of these seedling boards is to prevent them from moving due to wind and rain after they are installed, or to prevent them from slipping when used on slopes like those found in many plantations. Generally, pile holes 5 as shown in the figure are provided at various locations, and stakes are driven into these holes to fix the structure to the ground surface.

This seedling board is originally intended to protect the seedlings from the above-mentioned weeds and animals until they become young trees after 5 to 6 years. If they disappear, it would be a shame in terms of the manpower required to remove them and the preservation of the beauty of the forest.

Now, the corrosion of steel materials throughout Japan is classified by various environments (
rural, industrial, coastal areas), for example,
According to the ``Rust and Corrosion Prevention Manual for Steel Structures,'' as shown in Figure 2, corrosion is low in northern Hokkaido, and corrosion is considerably high in hot and humid regions from Kinki to western Kyushu.

In addition, in the legend of the same figure, "mdd" means "m9/di/
d a y J.

In addition, as shown in Figure 3, the aging of corrosion of ordinary carbon steel in rural areas tends to be severe for the first four years and then moderate, and the average amount of corrosion over a six-year period is From Figure 3, it is 100~/ml, or 0.
The amount of corrosion is 13mm.

This value is the average amount of corrosion, and in normal cases, local corrosion progresses to the weak points of the steel material, causing pitting corrosion and local corrosion. It is said to be ~5 times as long, so if we consider the 6-year service life, it will be 0.
．． A plate thickness of 49 to 0.65 mm is required.

From this point of view, it would be possible to process a cold-rolled steel plate with a thickness of 0.5 to 0.6 mm and use it as a seedling board, but this is not desirable from the point of view of protecting iron resources and cost. So,
The key point is how to reduce the thickness of the cold-rolled steel sheet and maintain uniform corrosion without localized corrosion by combining surface treatment methods according to the purpose.

As is well known, the methods of imparting corrosion resistance to steel materials include: - Adding alloying elements as in stainless steel and weathering steel; - Metal coating as in tinplate and galvanized iron; - Organic coating as in painting and laminating. There are two methods: (2) a method using an inorganic coating such as enamel or mortar; in particular, galvanized steel is a typical method that is used in extremely large quantities for automobiles, home appliance wires, shaped steel, etc.

However, apart from thick galvanizing by hot-dip dipping, thin galvanizing by electroplating (10 to 30 g/
m'), for example, according to the measurement results in the United States, as shown in Table 1, the zero
．． 042 mil/y vs. 0.034 mil/y for zinc
The corrosion resistance is only A/y, and the amount of zinc lost per year is 0.85 μ (6 g), and the basis weight of about 10 g can only guarantee about 2 years.

Kearey *N-J- value Moreover, when such a galvanized steel plate is used as a seedling board, while zinc is present on the surface, the metallic luster of the galvanized coating is retained to some extent, and as a result, the metal shines between the edges of the trees. This results in a scene with a mixture of foreign substances, which is undesirable from the standpoint of preserving the natural beauty.

On the other hand, there are other problems with seedling boards made of plastic or the like.

In other words, if plastic with excellent weather resistance is used, there will be no problem with its service life, but even after the mission of the seedling board is completed, it is difficult to corrode, so in some cases it may be necessary to remove it artificially so as not to hinder the growth of the trees. Even when the need arises, and even when there is no such need, if left as is, it will remain as "garbage" in the forest, and removing and incinerating it will require considerable manpower and expense.

Furthermore, regarding the conventionally used painted seedling boards that are painted and colored to match the natural environment, it is possible to paint each seedling board, ignoring the manpower and cost, but it is possible to paint each seedling board with a color that matches the natural environment. It will cost several times more to paint,
This is not a desirable method from an economic standpoint.

The present inventors have taken advantage of the advantages of metals such as zinc, which have a sacrificial anode effect on steel materials, and have systematically applied metal plating that has a stable film similar to natural rust without metallic luster on the surface. As a result of our research, we found that a material coated with manganese and on which a layer of oxygen-containing manganese compound was formed had the best corrosion resistance, and also had surprisingly well-balanced properties as described below. I discovered that.

Needless to say, since manganese is a metal that is electrochemically more base than zinc, as is clear from the natural electrode potential series in an aqueous solution of the metal, its corrosion resistance is naturally expected to be inferior to that of zinc. There has been no research or technology that attempts to directly improve the corrosion resistance of steel by coating it with manganese, except for inventions by the present inventors for other purposes.

(JP-A-50-136243, JP-A-5L-25975
) The chemical reactivity of metal manganese is more intense than that of zinc, and the purpose of these prior inventions is to utilize this property to improve chemical conversion treatment properties and use it as a steel sheet for painting base. However, it does not actively form an oxygen-containing manganese compound on the upper layer of the manganese plating layer.

More specifically, when metallic manganese is deposited by electroplating using a normal sulfuric acid bath, the metallic manganese combines with oxygen in the air, and for example, a thin film of manganese hydroxide formed during electroplating is oxidized in the air. This reaction forms an oxygen-containing manganese compound, which is poorly soluble in neutral salt solutions and water, resulting in a stable corrosion-resistant film that is completely different from metallic manganese.

In this way, the corrosion resistance of manganese plating does not lie in the manganese metal itself, but in the oxygen-containing manganese compound formed on top of it. The objective is to continuously regenerate the protective film in a self-repairing manner in response to loss.

Therefore, by applying electrolytic manganese plating to the steel surface, rinsing with water, and then drying, the steel material has an oxygen-containing manganese compound formed on the manganese plating.Even if the steel material is left in a corrosive environment, the corrosion-inhibiting effect of the oxygen-containing manganese compound is significant. It exhibits corrosion resistance, and the color tone of the protective film (corrosion product) of manganese that is formed in a natural corrosive environment is
Its brown color is the same as that of the soil, and after the manganese corrodes and disappears over many years, it has the advantage of returning to its natural state as the natural iron rust (brown) of the cold-rolled steel sheet material.

Therefore, if a seedling board is manufactured using such a steel material, it will be convenient as described above and will provide better results than any conventionally known material.

The present invention was made based on the above findings, and the gist thereof is to apply an oxygen-containing manganese compound to a thickness of 400 to 1000 on the surface of a cold-rolled steel plate with a thickness of 50 to 150μ. A seedling board side steel material is characterized in that a manganese plating layer having a thickness of 0.2 to 1 μm is formed on the upper layer.

The present invention will be explained in detail below.

First, the thickness of the cold-rolled steel plate used as the material in the present invention is 50~
As is clear from the above-mentioned Figure 3, the reason for setting it to 150μ is that
5 to 5 in normal rural areas in the presence of manganese plating layer
A thickness of 150μ is required to last for 6 hours, whereas in areas with relatively mild corrosive environments as shown in Figure 2, a thickness of 50μ is required to last the same amount as above, so the range of thickness of cold rolled steel sheets is was set to 50 to 150μ.

Next, regarding the thickness of the manganese plating layer, from the viewpoint of corrosion resistance, the thicker the layer, the better the corrosion resistance.However, the role of manganese is that the oxygen-containing manganese compound of the above-mentioned highly corrosion-resistant coating is in a corrosive environment. The purpose is to continuously replenish the protective film in a self-repairing manner through the interaction of corrosive substances (for example, water, oxygen, carbon dioxide, etc.).

Therefore, when directly coating a steel material with a manganese plating layer, the minimum thickness is sufficient to sufficiently cover the surface of the steel material, and is determined depending on the required corrosion resistance. Required minimum plating thickness: 0.
1μ, and the thickness of the oxygen-containing manganese compound formed immediately after plating varies from 0.04μ to 0.04μ depending on the plating conditions and heating drying conditions.
Since the thickness varies between 0.1μ, the lower limit of the plating thickness should be 0.2μ or more (1,!l/m2) in consideration of this.

Further, regarding the upper limit of the thickness of the manganese plating layer, 1μ (,7,39/m) is sufficient in terms of the service life of the seedling board.

The thickness of the oxygen-containing manganese compound formed on the upper layer of the manganese plating layer varies depending on electrodeposition conditions, chemical or heat treatment.
pectroscopy for chemical
Anal-ysis) 40 based on other measurement results
The required range is 0 to 1000 people.

If the thickness is less than 400λ, a uniform and continuous oxygen-containing manganese compound layer will not be formed, resulting in non-uniformity in its corrosion resistance.On the other hand, if it exceeds 1000A, peeling may occur during processing. be.

The formation of the manganese plating layer described above can be easily carried out by electroplating using an ordinary sulfate bath or chloride bath, as shown in Examples below.

Further, the formation of an oxygen-containing manganese compound can be obtained by washing with water immediately after the manganese plating and further drying and heating at a temperature of 40 to 250° C. for several seconds.

In addition, the production of the seedling board related to the present invention has a thickness of 50 to 15 mm.
This can be easily carried out by forming the manganese plating and the oxygen-containing manganese compound on an ultra-thin cold-rolled steel strip having a thickness of 0 μm, and then cutting and punching it into a seedling board of a certain shape.

Further, manganese plating and oxygen-containing manganese compound may be applied to a single seedling board that has been cut into a certain shape in advance, but it is obvious that the former method is easier to mass-produce on an industrial scale.

In this case, corrosion of the cut surface is a concern, but a feature of the steel of the present invention is that the sacrificial anode effect of manganese protects non-plated surfaces such as cut surfaces from the surroundings, so it is extremely effective. It becomes convenient.

EXAMPLES The effects of the present invention will be explained in more detail below using Examples.

Example: 100 g/l of manganese sulfate and 75 g/l of ammonium acetate were added to an ultra-thin cold-rolled steel plate with a thickness of 0.1 mm (100 μ).
Ammonium L thiocyanate 60 E/11 electrolytic bath (
1) H4, 2) bath temperature 25℃, current density 20A/dm
Under the conditions of 2, manganese plating was applied to various thicknesses using Pb-8n (5%) as a counter electrode, followed by washing with water and drying with hot air to form an oxygen-containing manganese compound.

Comparative materials: Salt spray tests (JIS-Z-
Corrosion resistance was compared using 2371).

Table 2 shows the test results.

In this table, the steel materials for seedling boards related to the present invention are marked with ◎, which exhibits extremely superior corrosion resistance compared to galvanized steel, and those with a plating thickness of approximately 0.5 μm are sprayed with salt water for a long time of 250 hours. No iron rust occurred after the test.

In addition, the steel material for seedling board of the present invention having a plating thickness of 1μ is 5μ.
Even after 00 hours of salt spray testing, there was no red rust due to iron rust.The comparative material was a 137g/771" hot-dip galvanized steel sheet coated with an epoxy primer and a silicone polyester topcoat (thickness: 25μ). It showed exactly the same corrosion resistance as galvanized iron.

The 500 hours of salt spray test mentioned here refers to the 5-year guarantee under any environment for the so-called 2-coat, 2-bake colored galvanized iron coated with an undercoat and topcoat on top of the hot-dip galvanized (1379/m' zinc coating on one side). As shown in Table 2, iron rust began to appear on the seedling board side steel material of the present invention after 500 hours of the salt water spray test, which corresponds to the 5 years when the seedlings had just begun to grow. This was very convenient because the thickness of the steel plate itself caused corrosion to progress over a period of 1 to 3 years, rusting, and disappearing naturally.

On the other hand, other comparative materials (with the exception of colored galvanized iron L) rust quickly and disappear before the period required to achieve the purpose of raising seedlings, or conversely, like colored galvanized iron, they last forever. Did not disappear (probably 20-3
Year 0) All of these materials were unsatisfactory as seedling board materials, as they deviated from their original purpose.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an outline of a seedling board, Figure 2 is a diagram showing the corrosion distribution of ordinary steel materials in Japan, and Figure 3 is a diagram showing changes over time in the amount of corrosion of various steel materials in rural areas. 1... Seedling board, 2... Hole, 3...
...Notch, 4 seedlings, 5...Pile hole.

Claims (1)

[Claims] 1. On the surface of a cold-rolled steel plate with a thickness of 50 to 150μ,
A steel material for a seedling board, characterized in that a manganese plating layer with a thickness of 0.2 to 1 μm is formed on the upper layer of an oxygen-containing manganese compound of 0 to 1000 people.